More often than not described as the last exhale of breathe, heard from the vibration of the neck when it is in an unusual position, allowing air to escape a narrow passage from the throat. It causes any of infinite odd sounds of expulsion of air.

You can imitate a death rattle for fun. Lean your neck backwards at 90 degrees and Pronounce terms such as "Ughrghrghrghrgh" or "Phhztttttt"